The first phase of this study has demonstrated that patients with metastatic disease have higher levels of energy expenditure than controls, and patients with extremity sarcomas have slightly higher levels of energy expenditure than controls. The next phase will determine if glucose oxidation, whole body protein turnover and potassium 40 levels are different in preoperative sarcoma patients from controls. Sarcomas are useful for understanding the pathophysiology of cachexia in that they usually do not alter the patient's ability to aliment himself, they are metabolically active and patients bearing them have been shown to have an increase in glucose consumption across tumor-bearing limbs. Stable isotopes in the forms of 13C-glucose and 15N-glycine and 13C-leucine are not radioactive and are very safe to administer. The study will determine if any difference demonstrated by measurements of isotopes can be correlated with tumor size or growth.